The present invention relates to a porous electrode, which electrode contains a porous, electrically conductive layer and an electrically conductive grid which serves as collector.
Electrodes of this type can be applied especially in fuel cells. During operation, the fuel employed will penetrate into the pores of the porous layer, which, as a rule, contain a catalytically active material for catalizing the galvanic combustion of the fuel. Generation of electric current takes place throughout the porous layer and the current generated is absorbed by the electrically conductive grid and carried off. The electrode is in contact with a suitable electrolyte which closes the current circuit within the fuel cell and with which also the reaction products of the electrode reactions occuring at the cathode and the anode can be discharged.
A considerable drawback of presently known porous fuel-cell electrodes is their high internal resistance, which has an unfavorable influence on the efficiency of current generation. In principle, internal resistance of the electrode might be reduced by decreasing the mesh width of the collector gauze. Such an approach will not effectively solve the problem, however, since the accessibility of the electrode surface and/or the pore walls becomes insufficiently large resulting in additional problems. In practice, collector gauze is applied having a wire thickness of about 300 .mu.m and a mesh width of 700 .mu.m or a corresponding perforated metal plate.
The present invention describes a porous electrode for a fuel cell wherein good accessibility of the catalytically active material is retained but where the internal resistance of the electrode is substantially reduced. According to the invention, a porous electrode which electrode contains a porous, electrically conductive layer and an electrically conductive grid which serves as collector, is characterized in that on or in the porous layer there are very thin fibres of an electrically conductive material.
Thus, it is an object of the present invention to provide a more highly efficient porous electrode.
Another object is to provide a porous electrode having a substantially reduced internal resistance without detrimentally affecting the porosity of the electrode.
Various other and more detailed objects and advantages of the invention, such as arise in connection with carrying out the above-noted ideas in a practical embodiment will become more readily apparent and will, at least in part, be hereinafter stated as the specific detailed description of the invention proceeds.